1. Field of the Invention
The present invention relates to a head suspension having a piezoelectric element that is attached to the head suspension with an adhesive and deforms in response to a voltage applied thereto.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing and needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
The magnetic disk drives have an urgent issue to solve, i.e., increasing storage capacity. The storage capacity of a magnetic disk drive will increase if the storage capacity of each magnetic disk contained in the magnetic disk drive increases. The storage capacity or recording density of a magnetic disk will increase, without changing the diameter thereof, if the number of tracks per inch (TPI) on the magnetic disk increases. For this, the width of each track on the magnetic disk must be narrow. To handle such narrow tracks on a magnetic disk, a magnetic head of a head suspension in the magnetic disk drive must conduct precise positioning in a direction across the tracks. For realizing the precise positioning, there is a need of an actuator capable of accurately moving and positioning the magnetic head of a head suspension within a very small area.
To meet the need, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-50140 a head suspension for a disk drive, including a base plate, a connection plate having a hinge thinner than the base plate, a load beam provided with a flexure and a magnetic head, and a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for a positioning purpose, a voice coil motor and the piezoelectric elements made of PZT (lead zirconate titanate).
The piezoelectric elements minutely drive a front end of the load beam in a widthwise direction (sway direction) of the head suspension. Compared with a single actuator system employing only a voice coil motor, the dual actuator system employing the voice coil motor and piezoelectric elements more precisely positions the magnetic head attached to the front end of the head suspension.
An important issue for the head suspension employing the dual actuator system is how to mount the piezoelectric elements on the head suspension.
As an approach to address the issue, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-184140 (in particular, an adhesive 80 in FIGS. 4 and 9) a head suspension for a disk drive having a load beam, a flexure attached to the load beam, an actuator base including a base plate, and a pair of piezoelectric elements. The actuator base has an opening in which the pair of piezoelectric elements is installed with an electrically insulative adhesive.
According to this related art, the piezoelectric elements are set at a predetermined position on the actuator base with a gap being secured between the piezoelectric elements and the actuator base and the adhesive is applied into the gap.
If the quantity of the adhesive applied into the gap is too small, a bonding strength will be insufficient to correctly transmit a displacement of the piezoelectric elements to the load beam. If the adhesive quantity is too large, the applied adhesive will ooze and spread. If the spread adhesive reaches the flexure of the load beam, it will deteriorate the rigidity balance and vibration characteristic of the head suspension.